It is conventional to "resurface," so to speak, surfaces of a variety of metal products when such surfaces become worn or are otherwise incapable of structurally performing their intended functions. For example, in U.S. Pat. No. 2,912,562 issued on Nov. 10, 1959 to George C. Donovan, a method is disclosed for depositing weld metal by electric arc welding over the entire inner surface of a cast iron cylinder liner used in railroad locomotives. Such cylinder liners are generally made from relatively soft cast iron and are mounted for rotation about a central axis thereof upon a lathe which also includes a lathe carriage for reciprocating the cylinder parallel to its axis. A welding wire (core and flux) is supported interiorly of the cylinder and is supplied appropriate welding current during the rotation and reciprocation of the cylinder which places what amounts to a weld deposit in the form of a helical, slightly overlapping bead upon the interior surface of the cast iron cylinder liner. The thus reconditioned cylinder liner can then be re-bored or otherwise machined to its original diameter for subsequent use.
As another example, U.S. Pat. No. 3,985,995 granted on Oct. 12, 1977 to Herman Th. Brandi discloses a method of manufacturing large diameter metal shafts for turbines and electric generators by feeding welding electrode from a storage reel to a core upon which molten metal is built-up along a spiral track. The core is rotated as the welding head travels axially, thus forming layer-upon-layer of helical beads to form the main body of a shaft.
In U.S. Pat. No. 4,660,756 granted on Apr. 28, 1987 to Max Geissler, a cylindrical member is rotated about its axis as its interior is built-up by the formation of a continuous helical welding bead In this case cooling water is sprayed through atomizer nozzles onto the inside wall which is being welded with excessive water being collected and removed by a pump.
It is also conventional to utilize multi-layer build-up welding to manufacture annular components, as evidenced by U.S. Pat. No. 4,671,448 granted Jun. 9, 1987 to Karl Million et al. An annular component upon which weld material is to be deposited is supported upon a turntable inclined to the horizontal which is rotated relative to a welding head for progressively building up weld material along an annular face of the annular component.
The utilization of cooling water which is brought into contact with a hot weld in a restricted zone located immediately under the molten bath is also well known from U.S. Pat. No. 3,948,428 granted on Apr. 6, 1976 to Franco Bonomo et al.
U.S. Pat. No. 4,230,928 granted Oct. 28, 1980 to Harvey W. Janssen is specifically directed to a machine for rebuilding worn tractor roller assemblies by depositing hard metal on the rim of the assembly while the assembly is rotated and cooled by circulating coolant therethrough.
U.S. Pat. No. 4,857,694 granted on Aug. 15, 1989 to Thomas E. Doyle et al. discloses an apparatus for automatically cooling a workpiece during its rotation as the workpiece is being externally built-up by applying a weld bead thereto through an associated welding head. The temperature is sensed in the vicinity of the welding head to generate appropriate coolant flow with appropriate control system programming being accomplished through a conventional computer or microprocessor control system, such as an IBM PC.
In the August 1993 publication of the WELDING JOURNAL there appears at pages 39 through 44 an article entitled "Unraveling the Mystries of Welding Cast Iron" by S. D. Kiser and Bob Irving. The article specifically states "white iron is a cast iron in which substantially all of the carbon is in solution and in the combined form. The metal has a white fracture surface when broken. It is considered to be unweldable by conventional processes." (See page 39.) Table 1 depicts the effect of microstructure and graphite morphology on the weldability of various cast irons, and indicates that white iron (cementite matrix) essentially lacks graphite and because of its approximate 0% elongation, it is incapable of being welded by virtually any known welding process because such "structures have little to no graphite inclusions and have no plastic ductility to resolve the stresses imposed by welding thermal cycles. These irons are considered to be unweldable by most fusion processes." (See page 41.) The article makes specific reference to welding a variety of products, such as repairing a gray iron take-up drum, a gray iron piercing ram for an extrusion press, carbon steel steering tubes and carbon steel heat exchanger shelves and tubes, but no examples of successful welding or surfacing of white iron or white cast iron is found in this article which reflects the conclusion earlier quoted from this article, namely, white iron "is considered to be unweldable by conventional processes." (See page 39.)
The foregoing reflects the conventionality of welding products, including rotating and translating a product relative to a welding head to build-up a surface of the product by applying thereto a generally continuous welding bead. However, in virtually all cases, the metal product is made of relatively soft metal, and though harder metal may be applied thereto, heretofore there has been no method known to the inventor for applying a welding bead to extremely hard metal, such as "chilled white iron." Products such as wear plates or suction plates for large hydraulic pumps in sizes ranging between 20 inches and 36 inches in outside diameter are made from chilled white iron, and once worn out, such plates were simply removed and replaced because heretofore efforts at building-up the same up through welding was not perceived possible. However, in accordance with the present invention, a novel method has been provided whereby a weld bead is placed continuously upon a surface of chilled white iron products, such as the aforementioned wear plates and suction plates, to effectively recondition the same for reuse, as opposed to being heretofore discarded.